CPU 312, the smallest S7-300 CPU. This is ideally suited to simple applications in which the advantages of TIA such as integrated communication, data management and diagnostics can however be utilized. Networking is possible using MPI or by means of CPs, the standard mode of application is, however, non-networked operation. The I/O is normally connected in a centralized configuration.

Siemens PLC S7-300 Product Specifications:

Article number	6ES7312-1AE14-0AB0
	CPU312, 32KB
General information
HW functional status	1
Firmware version	V3.3
Engineering with
● Programming package	STEP 7 V5.5 + SP1 or higher or STEP 7 V5.2 + SP1 or higher with HSP 218
Supply voltage
Rated value (DC)	24 V
permissible range, lower limit (DC)	19.2 V
permissible range, upper limit (DC)	28.8 V
external protection for power supply lines (recommendation)	2 A min.
Mains buffering
● Mains/voltage failure stored energy time	5 ms
● Repeat rate, min.	1 s
Input current
Current consumption (rated value)	650 mA
Current consumption (in no-load operation), typ.	140 mA
Inrush current, typ.	3.5 A
I²t	1 A²·s
Power loss
Power loss, typ.	4 W
Memory
Work memory
● integrated	32 kbyte
● expandable	No
Load memory
● Plug-in (MMC)	Yes
● Plug-in (MMC), max.	8 Mbyte
● Data management on MMC (after last programming), min.	10 y
Backup
● present	Yes; Guaranteed by MMC (maintenance-free)
● without battery	Yes; Program and data
CPU processing times
for bit operations, typ.	0.1 µs
for word operations, typ.	0.24 µs
for fixed point arithmetic, typ.	0.32 µs
for floating point arithmetic, typ.	1.1 µs
CPU-blocks
Number of blocks (total)	1 024; (DBs, FCs, FBs); the maximum number of loadable blocks can be reduced by the MMC used.
DB
● Number, max.	1 024; Number range: 1 to 16000
● Size, max.	32 kbyte
FB
● Number, max.	1 024; Number range: 0 to 7999
● Size, max.	32 kbyte
FC
● Number, max.	1 024; Number range: 0 to 7999
● Size, max.	32 kbyte
OB
● Number, max.	see instruction list
● Size, max.	32 kbyte
● Number of free cycle OBs	1; OB 1
● Number of time alarm OBs	1; OB 10
● Number of delay alarm OBs	2; OB 20, 21
● Number of cyclic interrupt OBs	4; OB 32, 33, 34, 35
● Number of process alarm OBs	1; OB 40
● Number of startup OBs	1; OB 100
● Number of asynchronous error OBs	4; OB 80, 82, 85, 87
● Number of synchronous error OBs	2; OB 121, 122
Nesting depth
● per priority class	16
● additional within an error OB	4
Counters, timers and their retentivity
S7 counter
● Number	256
Retentivity
— adjustable	Yes
— lower limit	0
— upper limit	255
— preset	Z 0 to Z 7
Counting range
— lower limit	0
— upper limit	999
IEC counter
● present	Yes
● Type	SFB
● Number	Unlimited (limited only by RAM capacity)
S7 times
● Number	256
Retentivity
— adjustable	Yes
— lower limit	0
— upper limit	255
— preset	No retentivity
Time range
— lower limit	10 ms
— upper limit	9 990 s
IEC timer
● present	Yes
● Type	SFB
● Number	Unlimited (limited only by RAM capacity)
Data areas and their retentivity
Retentive data area (incl. timers, counters, flags), max.	32 kbyte
Flag
● Size, max.	256 byte
● Retentivity available	Yes; MB 0 to MB 255
● Retentivity preset	MB 0 to MB 15
● Number of clock memories	8; 1 memory byte
Data blocks
● Retentivity adjustable	Yes; via non-retain property on DB
● Retentivity preset	Yes
Local data
● per priority class, max.	32 kbyte; Max. 2 KB per block
Address area
I/O address area
● Inputs	1 024 byte
● Outputs	1 024 byte
Process image
● Inputs	1 024 byte
● Outputs	1 024 byte
● Inputs, adjustable	1 024 byte
● Outputs, adjustable	1 024 byte
● Inputs, default	128 byte
● Outputs, default	128 byte
Digital channels
● Inputs	256
— of which central	256
● Outputs	256
— of which central	256
Analog channels
● Inputs	64
— of which central	64
● Outputs	64
— of which central	64
Hardware configuration
Number of expansion units, max.	0
Number of DP masters
● integrated	0
● via CP	4
Number of operable FMs and CPs (recommended)
● FM	8
● CP, PtP	8
● CP, LAN	4
Rack
● Racks, max.	1
● Modules per rack, max.	8
Time of day
Clock
● Software clock	Yes
● retentive and synchronizable	No; Buffered: No, Can be synchronized: Yes
● Deviation per day, max.	10 s; Typ.: 2 s
● Behavior of the clock following POWER-ON	the clock continues at the time of day it had when power was switched off
Operating hours counter
● Number	1
● Number/Number range	0
● Range of values	0 to 2^31 hours (when using SFC 101)
● Granularity	1 h
● retentive	Yes; Must be restarted at each restart
Clock synchronization
● supported	Yes
● to MPI, master	Yes
● to MPI, slave	Yes
● in AS, master	Yes
● in AS, slave	No
Digital inputs
Number of digital inputs	0
Digital outputs
Number of digital outputs	0
Analog inputs
Number of analog inputs	0
Analog outputs
Number of analog outputs	0
Interfaces
Number of industrial Ethernet interfaces	0
Number of PROFINET interfaces	0
Number of RS 485 interfaces	1; MPI
Number of RS 422 interfaces	0
1. Interface
Interface type	Integrated RS 485 interface
Isolated	No
Interface types
● RS 485	Yes
● Output current of the interface, max.	200 mA
Protocols
● MPI	Yes
● PROFIBUS DP master	No
● PROFIBUS DP slave	No
● Point-to-point connection	No
MPI
● Transmission rate, max.	187.5 kbit/s
Services
— PG/OP communication	Yes
— Routing	No
— Global data communication	Yes
— S7 basic communication	Yes
— S7 communication	Yes; Only server, configured on one side
— S7 communication, as client	No
— S7 communication, as server	Yes
Protocols
PROFIsafe	No
communication functions / header
PG/OP communication	Yes
Data record routing	No
Global data communication
● supported	Yes
● Number of GD loops, max.	8
● Number of GD packets, max.	8
● Number of GD packets, transmitter, max.	8
● Number of GD packets, receiver, max.	8
● Size of GD packets, max.	22 byte
● Size of GD packet (of which consistent), max.	22 byte
S7 basic communication
● supported	Yes
● User data per job, max.	76 byte
● User data per job (of which consistent), max.	76 byte; 76 bytes (with X_SEND or X_RCV); 64 bytes (with X_PUT or X_GET as server)
S7 communication
● supported	Yes
● as server	Yes
● as client	Yes; Via CP and loadable FB
● User data per job, max.	180 byte; With PUT/GET
● User data per job (of which consistent), max.	240 byte; as server
S5 compatible communication
● supported	Yes; via CP and loadable FC
Number of connections
● overall	6
● usable for PG communication	5
— reserved for PG communication	1
— adjustable for PG communication, min.	1
— adjustable for PG communication, max.	5
● usable for OP communication	5
— reserved for OP communication	1
— adjustable for OP communication, min.	1
— adjustable for OP communication, max.	5
● usable for S7 basic communication	2
— reserved for S7 basic communication	0
— adjustable for S7 basic communication, min.	0
— adjustable for S7 basic communication, max.	2
S7 message functions
Number of login stations for message functions, max.	6; Depending on the configured connections for PG/OP and S7 basic communication
Process diagnostic messages	Yes
simultaneously active Alarm-S blocks, max.	300
Test commissioning functions
Status block	Yes; Up to 2 simultaneously
Single step	Yes
Number of breakpoints	4
Status/control
● Status/control variable	Yes
● Variables	Inputs, outputs, memory bits, DB, times, counters
● Number of variables, max.	30
— of which status variables, max.	30
— of which control variables, max.	14
Forcing
● Forcing	Yes
● Forcing, variables	Inputs, outputs
● Number of variables, max.	10
Diagnostic buffer
● present	Yes
● Number of entries, max.	500
— adjustable	No
— of which powerfail-proof	100; Only the last 100 entries are retained
● Number of entries readable in RUN, max.	499
— adjustable	Yes; From 10 to 499
— preset	10
Service data
● can be read out	Yes
Ambient conditions
Ambient temperature during operation
● min.	0 °C
● max.	60 °C
configuration / header
Configuration software
● STEP 7	Yes; V5.2 SP1 or higher with HW update
configuration / programming / header
● Command set	see instruction list
● Nesting levels	8
● System functions (SFC)	see instruction list
● System function blocks (SFB)	see instruction list
Programming language
— LAD	Yes
— FBD	Yes
— STL	Yes
— SCL	Yes
— GRAPH	Yes
— HiGraph®	Yes
Know-how protection
● User program protection/password protection	Yes
● Block encryption	Yes; With S7 block Privacy
Dimensions
Width	40 mm
Height	125 mm
Depth	130 mm
Weights
Weight, approx.	270 g